Olefin polymerization process
View Patent ↗A polymerization process for copolymerizing ethylene and a series of α-olefins to form a branched polyethylene, in which the series of α-olefins is generated in-situ by an ethylene oligomerization catalyst, is improved if the oligomerization catalyst has a Schulz-Flory constant of about 0.30 to about 0.55. This makes very little higher molecular weight α-olefins, which allows for easy removal of unpolymerized α-olefins from the polyolefin product.
1. A process for the manufacture of a branched polyethylene, comprising, contacting ethylene with a copolymerization catalyst and an oligomerization catalyst that produces a series of α-olefins, wherein the improvement comprises, said oligomerization catalyst that produces said series of α-olefin having a Schulz-Flory constant of from about 0.30 to about 0.55 under process conditions.
2. The process as recited in claim 1 wherein said Schulz-Flory constant is from about 0.35 to about 0.50.
3. The process as recited in claim 1 wherein said copolymerization catalyst is a metallocene, a chromium, or a Ziegler-Natta catalyst.
4. The process as recited in claim 1 wherein said oligomerization catalyst is an iron complex of a ligand of the formula:
wherein:
R 1 , R 2 , and R 3 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or an inert functional group, provided that any two of R 1 , R 2 , and R 3 vicinal to one another taken together may form a ring;
R 4 and R 5 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or an inert functional group provided that R 1 and R 4 and/or R 3 and R 5 taken together may form a ring; and
R 6 and R 7 are each independently aryl or substituted aryl.
5. The process as recited in claim 4 wherein R 4 and R 5 are both methyl or hydrogen, or one of R 4 and R 5 is methyl and the other is hydrogen.
6. The process as recited in claim 4 wherein R 6 and R 7 are phenyl or substituted phenyl.
7. The process as recited in claim 1 wherein one or both of said copolymerization catalyst and said oligomerization catalyst are supported on support particles.
8. The process as recited in claim 7 wherein said copolymerization catalyst and said oligomerization catalyst are both supported on the same support particles.
9. The process as recited in claim 1 wherein said process is continuous.
10. The process as recited in claim 8 wherein said process is a gas phase, slurry, or solution process.
11. The process as recited in claim 4 wherein R 1 , R 2 , and R 3 are hydrogen and wherein R 6 is
and wherein R 7 is
and wherein two of R 4 , R 5 , R 8 , R 12 , R 13 and R 17 are independently methyl or ethyl and the remainder of R 4 , R 5 , R 8 , R 12 , R 13 and R 17 are hydrogen and wherein R 9 , R 10 , R 11 , R 14 , R 15 , and R 16 are each independently hydrogen, a functional group, hydrocarbyl, or substituted hydrocarbyl.
12. The process as recited in claim 1 wherein a catalyst that homopolymerizes ethylene but does not readily copolymerize ethylene and α-olefins is also present.
13. The process as recited in claim 2 wherein said oligomerization catalyst is an iron complex of a ligand of the formula:
wherein:
R 1 , R 2 , and R 3 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or an inert functional group, provided that any two of R 1 , R 2 , and R 3 vicinal to one another taken together optionally form a ring;
R 4 and R 5 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or an inert functional group provided that R 1 and R 4 and/or R 3 and R 5 taken together may form a ring; and
R 6 and R 7 are each independently aryl or substituted aryl.